1. Field of the Invention
This invention relates to a medical device which assists in the application of cricoid pressure (CP) during medical procedures such as intubation of the trachea or other airway management procedures where there is a concern of aspiration of gastric contents into the lungs or insufflation of air into the stomach causing gastric distension.
2. Discussion of the Prior Art
Doctors, nurses, paramedics, among others, frequently perform bag/mask ventilation or intubation of the trachea with an endotracheal tube. Such medical personnel frequently must secure the airway employing a rapid sequence intubation technique utilizing general anesthesia medications. In an emergency situation, the medical personnel will not know if the patient has a full-stomach. Patients who require advanced airway management services including bag/mask ventilation and rapid sequence intubation are at risk for aspiration of their gastric contents. Aspiration of gastric contents is associated with morbidity and potential mortality.
The application of pressure to the cricoid cartilage, also known as the Sellick maneuver, is the standard of care in the anesthesia community. The application of cricoid pressure has traditionally been accomplished manually, where a trained health care provider will use his or her fingers to apply the pressure. When indicated, before the induction of general anesthesia, the cricoid cartilage is palpated and held between the assistant's thumb and the second finger. The assistant's index finger is then used to apply pressure on the cricoid cartilage. As induction of general anesthesia is commenced, pressure is exerted on the cricoid cartilage, such that the cricoid cartilage is pushed up against the cervical vertebrae. The esophagus is thus occluded in an effort to prevent aspiration of gastric contents and insufflation of air into the stomach during positive pressure bag/mask ventilation.
Clinical research has determined that approximately 20 to 40 newtons of cricoid pressure is necessary to achieve esophageal occlusion, which effectively prevents regurgitation of gastroesophageal contents into the lungs of the patient. In terms of Newton's (N), the recommended force to be exerted before loss of consciousness is 20 N, or approximately 2 kg of force. The force is then increased to between 30 to 40 N, or 3 kg to 4 kg of force for an unconscious person.
Too much or too little force may put the patient at risk. Too much force may damage the trachea or other surrounding anatomical structures or may result in inadequate patient ventilation. Too little force on the cricoid cartilage undermines the efficacy of the procedure by failing to occlude the esophagus to prevent aspiration of gastric contents. Because of the importance of the amount of cricoid pressure, the person applying the pressure must know how to do so properly. Even a trained doctor, nurse, or paramedic, however, cannot objectively apply and maintain the proper pressure without some method of determining the cricoid pressure being applied.
An instrument designed to inform the user of the force being applied to the cricoid cartilage needs to be easy to place precisely, must provide accurate indications when the necessary force has been obtained, should not interfere with ventilation or intubation, and should cause very little trauma to the patient.
As a method of training healthcare providers in applying cricoid pressure, Carol A. Koziol, RN, et al, in AORN Journal Vol. 27, No. 6, (2000) suggests placing a model of a cricoid cartilage on a scale, and then measuring the force so that the healthcare provider can get a feel for what their actual performance should be in the perioperative setting. However, this method is only a training method, and does not provide an accurate indication of when the necessary force is being applied to an actual patient.
U.S. Pat. No. 5,483,974 granted on Jan. 16, 1996 to Richard Crangle entitled “Device To Apply, Hold, and Measure Cricoid Pressure During Entotracheal Intubation or Cricothyroidotomies, or Other Medical Airway Procedures” shows an arrangement where a contact cushion is disposed directly on the front of the neck, and held in place using an adjustable strap. Once the Crangle device is attached to the neck of the patient, the healthcare provider then applies pressure to the entire apparatus using his or her hands. When the device is employed, the surface of the device engages a bladder, creating pressure against the cricoid cartilage and the pressure is translated to a release valve and a dial indicator. If the force applied exceeds the recommended number of Newtons, a release valve will automatically depressurize the compressible bladder.
Crangle's approach, however, is both cumbersome, and difficult to use. First, the manufacture of such a device, which includes a bladder of suitable size, with a pressure gauge, and a release valve will necessarily result in a bulky device that is awkward for both the healthcare provider and the patient. Second, the device is not simple to use from the perspective of the healthcare provider. It is a two-step process of first attaching the device to the patient's neck, and then applying necessary force. In an emergency situation, the healthcare provider will be wasting precious time following these two steps, rather than using a device that requires only the step of applying force to the cricoid cartilage. Finally, from the perspective of the patient who is still conscious, having such a cumbersome device attached to his or her neck might be at best awkward, and at worst extremely uncomfortable, and traumatic.
European Patent Application, EP 1 043 040 A2, entitled “A Device For Use In The Application Of Cricoid Pressure (Force) and/or In Training For Such Application” discloses a plastic cylinder, a piston with a seal and an aneroid pressure gauge connected to the nozzle of the cylinder. The healthcare provider places the tip of the piston on the cricoid cartilage of the patient and then presses down on two wings on the cylinder with his index finger and thumb. The air pressure near the top of the cylinder is then measured indicating the amount of force being applied to the patient's cricoid.
This approach will, over time, become dangerously inaccurate. The seal necessary to capture the air pressure will, over time, begin to break down leading either to an inaccurate or useless reading. Attempts to sterilize the device will rapidly deteriorate the seal, also leading to inaccurate and useless readings. Furthermore, this device is not ergonomically sound from the perspective of the healthcare provider. In some instances, cricoid pressure must be maintained for over 30 minutes. In that time, the healthcare provider's fingers may become sore from the continuous application of pressure.
E. G. Lawes, et al, in the British Journal of Anaesthesia vol. 58 (1986) discloses a device which measures cricoid pressure by the closing of a circuit. The three essential elements of the device include a foam contact cushion, which is used to apply a force to the cricoid cartilage, a Perspex platform carrying a simple circuit, and stainless steel flexible wings. The healthcare provider grips the device with both hands with upturned end of the wings using his forefingers and thumbs. Once the contact cushion is applied to the patient's neck, the healthcare provider then presses down simultaneously on both wings. When a force of 44 N has been applied, a circuit on the Perspex platform is activated by means of a contact breaker.
The Lawes device is deficient in several ways. First, by requiring the healthcare provider to use both hands to apply pressure to the cricoid, she or he is not free to provide the necessary support to the back of the patient's neck. Without this support, the neck may flex forward and interfere with airway management. Second, the device only is designed to alert the user when a pressure of 44 N has been achieved. As previously mentioned, 44 N is only the appropriate limit on cricoid pressure for an unconscious patient. For a patient who is still conscious, the device does not alert the user when pressure of 20 N has been achieved.